Titanium pigment



Reiaued May 8, 1928.

UNITED STATES :osara BLUIENIELD, or

PATENT OFFICE.

LONDON, ENGLAND, ASSIGNOR, BY MESNE ASSIGNMENT8,-

'rrrmruu rromnnr.

I Drawing. Original 1T0. 1,504,678, dated-August 12, 1924, Serial No. 652,189, flied July 17, 1923.

Application for reissue filed August 9, 1926.

This invention relates to a process for transforming b physico-chemical means precipitated oxi e or hydroxide of titanium into a pigment which consists of either pure '5 oxide of titanium or of a mixture same with other substances, such as are usually employed as fillers, for example, barium sulphate, silica, kaolin and the llke.

The invention also relates to the pigments 1 obtained by means of this process. This pigment is characterized by a well defined state of division of all or part of the oxide or hydroxide of'titanium, sion confers on the igment particularly valuable properties or employment in paints, enamels and the like.

Among the characteristics which make the value of a pigment the covering power,

mechanical resistance of the film and 1ts ad hesive power, stability to light and to chemical agents, and miscibility with oil are gen 'erally specified. All these properties vary very rapidly with its state of division below any which can be obtained by 'OIdlIlBIY me--- i chanical grinding. This state of division thus is a fundamental characteristic of a good pigment.

All known processes for the preparation of a pigment with titanium compounds as base advocate the oxide or hydroxide of titanium being precipitated in a state which '.s convenient for theirbeing employed as a pigment, that is to say,

state of division. Inconveniences result from this which affect either the chemical side of the manufacture (separation from mother liquor, washing of precipitate and its purification, etc.), or the quality of the pigment itself (Impossibility of always obtaining the 40 same state of division and limit ofdegree of this state).

The problem of determining the fundamental causes for the variability of pigmentary qualities of different titanium oxides 46 has been investigated and it was found that this variability is connected with the size of the particles from which the oxide is formed. It has been verified that to obtain a good pigment it is nec ssary that the parof the which state of divi- Serial m. 128,328.

ticles be small, butit was discovered at the same time that it is indispensable that the particles should be of different sizes. Very good results are obtained when the micro scope shows that large and small particles have such a proportion both as to number and size that the space between them is as completely filled as possible, the smaller particles grouping themselves in the spaces between the larger, and thus securing the continuity and cohesion of the whole just in the same way as in the caseof concrete.

By the utilization of this principle a-still better pigment has been discovered and methods of securing with certainty the production thereof. In this pigment a certain proportional quantity of the oxide is in a state of division, characterized by the presence of particles which are both ultramicroscopic and smaller, giving-with linseed oil or other vehicles which can be employed, a colloidal solution. This colloidal solution after drying leaves a film which is exceptionally adhesive, owing to molecular forces coming into play. This film acts both as a sub-stratum and as an agglutinant for the larger particles of the pigment and thus secures opacity. 1

Another fundamental fact is that no ordinary treatment either of a mechanical or thermal nature is able tosub-divide the ultimate particles of titanium compounds once made by the wet method (i. e. by hydrolysis of sulphate solutions). In consequence,

these treatments cannot transform 1nto a pigment with the above characteristics, a precipitated oxide or hydroxide of titanium, which does not possess the required quellties. On the contrary, a precipitate possessing these particular qualities will preserve them through all the ordinarymechanical or thermal treatments.

The invention consists in producing colloid titanium compounds by the peptization of precipitated titanium compounds with suitable quantities of peptizing agents to give the .desired physical characteristics for various purposes.

The invention also consists in producing titanium pigments by the peptization of precipitated titanium compounds with suitable quantities of peptizin-gagents.

The invention further consists in producing titanium pigments by pe tization of titanium compounds precipitate from crystalloid solutions.

The invention also consists in transforming into pigment form, that is to say, conferring the abovefmentioned qualities on the colloidal. products of all compounds of titanium, metallic titanates, etc., capable of being converted into the "colloidal state, such as oxide or h droxide of titanium, precipitated by hydrolysis, by means of an operation which is carried out before drying and dehydration. This efl'ect is obtained by dispersing by processes of-gradual peptization of oxide or hydroxide cleared from its electrolyte when pure products are desired. This dispersion is afi'ected by means of small quantities of acid or alkali or salts of titanium, or of any substance which diminishes the surface tension of the liquid phase, causing dispersion. The operation takes'place before, during or after the o tional incorporation of substances usua 1y employed as fillers' Every new addition of'peptizing agent hasthe effect of increasing the degree of dispersion of the gel. Under these circumstances o it is easy to establish the quantity of the reagents necessary in order to produce the desired state ofdivision according'to what-' ever purpose the pigment is to be used for.

On general lines these oxides or hydroxides of titanium have the following properties:

1. Thinned out with water before drying they changeor at least a portion of them does-into a colloidal solution which has all the properties common to. such solutions, for example, they are unfiltrable, opalescent, give the ordinary ultra-microsco ic light efiects and are capable of coa u ation by means of the electrolytes especi y by polyvalent acids.

2. When dried or-dehydrated'they do not disintegrate into powder but .form clots which are easily reduced to powder bymechanical means.

a. This powder mixed with linseed 'oil.

' makes a paste which contains ultra-microscopic'al particles. Due to the resence of these particles the paste has in re ected light -a bluish colour or other colour according to the size of the particles, owin to the scattering of light by suspen ed particles. When dried in a th n layer the paste gives a ve adhesive film.

4. en exposed to the light in contact with or nic substances such as turpentine, essentiaFdils and the like they do not change co our.

Thiastability is due to the'fact that the pounds.

traces of soluble titanium compounds ha been eliminated. These soluble, compolmde under the action of light and of oxygen ,which'is made active by those organic sub- .stances whose catalytic power is known are yellow .pertitanic com converted into the Example-I.

1 kilogram of TiO, in the form of metatitanic acid precipitated by hydrolysis I and filtered is treated with ammon a in suflicient quantity to neutralize the sulphuric acid contained inthe precipitate. The sulphate of'a'mmonia formed is eliminated bywvashing. 20 grams of concentrated HCI are added. The mass becomes completely. fluid and the phenomena. of peptization occur. The whole is then dried and dehydrated and worked up into pigment with any suitable vehicle.

Example I I p 1 kilogram of acid hydroxide of titanium obtained *from sulphate by hydrolysis in known manner, is treated with chloride of barium in quantity equivalent to the sulphuric' acid contained in the hydroxide. Hydrochloric acid is liberated by this reaction, which also precipitates barium sulphate in the mass," forming acomposite pigment. The sulphuric acid being-transformed into an insoluble form, the peptization commences. The degree of dispersion can be decreased as desiredby partial substitution of chloride of bariumb'y carbonate .or sulphide, or silicate of barium or calcium,

known manner is neutralized by carbonate of sodium and the sulphate of sodium formed is washed out by water. The bydroxide of titanium is then dispersed to the desired degree by. adding chloride of titanium or chloride of siliconiand the whole is dried and dehydrated.

Emplellv.

To any pigment of poor quality which it is desired to improve er cent to per cent of titanium hydroxi e which has been already peptized as above is added. The addition has the efiect of improving to a very great extent the pigmentary qualities of the original pigment.

This process for preparing pigments of titanium base has the following advantages:-

1. It frees the v chemical treatment of preparing oxide or hydroxide of titanium from difliculties of purification which the manufacture of a pigment requires and confines the chemical treatment only to chemical puroses.

2.'It enables one to obtain withoutany limit the state of division of the material most suited for the pigment which is desired.

3. It enables one to fix quantitatively the state of division so as to .obtain the greatest efiect and to adjust this state of division to each particular need.

4. It enables one to change as desired in the pigment as above specified any constitutional element of its structure for another element with the same physical structure but of a difl'erent chemical composition such as sulphate of barium, silica. or other fillers.

Having now described my invention what I claim as new and desire to secure by Letters Patent is 1. Dehydrated peptized tetravalent titanium oxides.

2. A composition of matter comprising a 'peptized hydrolytically produced oxygen compound of titanium.

3. A process of forming titanium pigments which comprises precipitating a gel of titanic acid, peptizing said gel and drying and dehydrating said peptized gel;

4. An aqueous colloidal dispersion oi peptized' titanium dioxide.

' the precipitate, agent containing 5. A composition com rising colloidal particles of titanium dioxide pept-ized in water containing chlorine ions.

-6. An unfiltrable aqueous colloidal dispersion of titanium dioxide and a peptizing agent.

7 An unfiltrable opalescent colloidal solution characterized in containing peptized titanium dioxide and being free from sulfuric acid.- v v 8. A pigment containng dehydrated peptized titanium dioxide. Y v

9. A paint containing dehydrated peptized titanium dioxide colloidally dispersed in an organic vehicle.

.10. A process for producing. an aqueous colloidal dispersion of titanium dioxide which comprises associating a pa tizing agent with precipitated titanium oxide free from sulfuric acid. v

11. A, process for producing an aqueous colloidal dispersion of titanium dioxide which comprises hydrolyzing a titanium sulfate solution, removing adsorbed acid from and associating a peptizing chlorine ions with said precipitate. I

12. A process for producing. an aqueous colloidal dispersion of titanium dioxide which comprises hydrolyzing a titanium sulfate solution, removing adsorbed sulfuric acid from the precipitate and associating hydrochloric acid with said precipitate.

13. A process for producing'an aqueous colloidal dispersion of titanium dioxide which comprises hydrolyzing titanium sulfate and treating the precipitatewith the chloride of an alkaline earth metal.

JOSEPH BLUMENFELD. 

